A turbine housing for use in a turbo charger is generally produced by casting. On the other hand, a turbine housing partially made of a sheet metal is disclosed in Patent Literature 1. The turbine housing is illustrated in FIG. 8.
As illustrated in FIG. 8, a turbine housing 1 for a turbo supercharger includes an inner pipe 3 forming an exhaust air flow path in which a turbine wheel 2 is arranged and an outer pipe 4 spaced from the inner pipe 3 at a predetermined distance and covering the inner pipe 3.
To cause the outer pipe 4 to function as a breakage protection device, the outer pipe 4 is a multi-layered structure in which a plurality of metal thin plates 4a to 4d are laminated between a back plate 5 and an opening end 3a of the inner pipe 3, and breaking strength of the outer pipe 4 is heightened.